Microservice practice | fuse hytrix initial experience

What is? Hystrix

In daily electricity consumption , If the fuse is correctly placed in our circuit , Then when the voltage rises abnormally , The fuse will blow to cut off the current , So as to protect the safe operation of the circuit .

In the cargo ship , In order to prevent the spread of water leakage and fire , Generally, the warehouse will be divided , To avoid the tragedy of a warehouse accident leading to the sinking of the whole ship , This is the bulkhead protection mechanism .

Hystrix The fuse provided is similar , When calling a service provider , When the total number of requests exceeds the configured threshold in a certain period of time , And the error rate is too high in the window period , that Hystrix The call request will be fused , Subsequent requests are short circuited directly , Enter degradation logic , And implement the local degradation strategy .

meanwhile Hystrix It also isolates the service providers in the system , A service provider delays too much or fails , It doesn't lead to the failure of the whole system , At the same time, it can also control the concurrency of calling these services .

All in all ,Hystrix Can disable your system in the event of a dependency service failure , By isolating the services on which the system depends , Prevent service cascading failure , It also provides a failback mechanism , Deal with failures more gracefully , And enable your system to recover from exceptions more quickly .

Hystrix actual combat

Then, in our last article dms service , Make the following changes ：

Feign Support by itself Hystrix, There is no need to introduce additional dependencies .

1、 First modify the caller app The configuration file for the service application.xml, Turn on hystrix

feign:
 hystrix:
  enabled: true

2、 Add service fuse processing , Realization DmsApi Interface

/** * @Author: official account ： The programmer 965 * @create 2022-06-26 **/
@Component
public class DmsHystrixImpl implements DmsApi {
    
    @Override
    public String findNameByCode(String code) {
    
        return " Server failure ";
    }
}

3、 Modify the interface class annotation , Add fusing treatment ：fallback = DmsHystrixImpl.class;

（Spring Cloud Feign HTTP Request exception Fallback Fault tolerance mechanism , It is based on Hystrix Realized , So you need to configure parameters feign.hystrix.enabled=true Enable this function ）

/** * @Author: official account ： The programmer 965 * @create 2022-06-20 **/
@FeignClient(value = "dms",fallback = DmsHystrixImpl.class)
public interface DmsApi {
    
    @RequestMapping(value="/dict/{code}", method = RequestMethod.GET)
    public String findNameByCode(@PathVariable("code") String code);
}

4、 Add exception code , In order to verify

/** * @Author: official account ： The programmer 965 * @create 2022-06-20 **/
@RestController
public class DmsController implements DmsApi {
    

    @Override
    public String findNameByCode(String code) {
    
        Integer.parseInt("a");
        switch (code){
    
            case "0" :
                return " male ";
            case "1" :
                return " Woman ";
            default:
                return " Unknown ";
        }
    }
}

5、 Start project , To verify , Return the correct result .

summary

In the microservices architecture , There are usually multiple services calling each other , A failure of the underlying service can lead to cascading failures , And then the whole system is not available , This phenomenon is called service avalanche effect . The service avalanche effect is a result of “ Service providers ” The unavailability of “ Serving consumers ” Not available , And will not be available for gradual amplification of the process .

Such as ：A As a service provider ,B by A Service consumers ,C and D yes B Service consumers .A Unavailability caused B Not available , And enlarge the unavailable as snowball to C and D when , The avalanche effect is formed . In order to avoid the formation of avalanche effect , You need to use Hystrix.